Trials of two new drugs, invermectin (Phase IIa) and CGP-20376 (Phase I), are being initiated in collaboration with investigators from Madras India for patients with bancroftian filariasis. Since bronchoalveolar lavage studies on patients with tropical pulmonary eosinophilia show persistent alveolitis despite standard therapy with diethylcarbamazine (DEC), a trial comparing long-term DEC or DEC plus steroids with standard therapy has commenced. Clinical evaluation of Peace Corps Volunteers working in Central/West Africa indicates that when such expatriates enter Loa loa endemic areas, they become immunologically hypersensitive to the parasite and often develop severe clinical symptoms. To develop means for protecting such individuals from infection, a double-blind trial of prophylactic weekly DEC is now in its second year.